Aqueous herbicidal agent

ABSTRACT

A herbicidal agent comprising: (1) water; (2) ioxynil and/or a derivative thereof; (3) a compound of the formula (I) 
     
       
         RO—(CH 2 H 4 O) n (CH 3 H 6 O) m —R′  (I) 
       
     
     wherein RO is an alcohol radical selected from the group consisting of branched or linear, saturated or unsaturated monohydric alcohols having from 1 to 6 carbon atoms, or a polyol radical having from 2 to 12 carbon atoms and from 2 to 6 hydroxyl groups; R′ is hydrogen or an ester group —CO—R″ wherein R″ is a branched or linear, saturated or unsaturated alkyl radical having 5 to 29 carbon atoms, n is a number between 1 and 50 and m is zero or a number between 1 and 10. The herbicidal agents permit high penetration of the herbicide into the plant.

The present invention relates to aqueous herbicidal agents whichcomprises at least one agrochemical active ingredient from the groupconsisting of ioxynil and derivatives thereof, and certain alkoxylatedfatty acid esters, to the use of such fatty acid esters for increasingthe penetration of ioxynil or derivatives thereof into the leaves ofplants, and to a method of controlling undesired plant growth.

To control weeds, a large number of herbicidal substances are knownwhich frequently exhibit only low or no solubility in water. Animportant representative is ioxynil (3,5-diiodo-4-hydroxybenzonitrile)and derivatives thereof. During application of these active ingredients,the low solubility in water means that penetration into the plant isonly low and thus the herbicidal action is inadequate. Such agrochemicalactive ingredients are therefore formulated in the form of an aqueousdispersion or emulsion and can then be used without problems, e.g. byspraying onto the plants, where the emulsifier also functions as awetting agent and permits improved uptake of the active ingredient intothe plant. The higher the penetration of the active ingredient, the moreeffectively and efficiently it can be used. There is therefore generallya need for formulations which permit the greatest possible penetrationof the herbicidal active ingredient into the plant. DE-A 29 24 403discloses, for example, aqueous agents which comprise ioxynil salts and,as formulation auxiliaries, alkali metal salts of alkyl polyglycol etherphosphate partial esters. EP-0-485 207 discloses aqueous emulsionscomprising ioxynil octanoate and heptanoate which comprise polyalkyleneoxide-modified silanes or ethoxylated tall oil amides as emulsifiers.Surprisingly, it has been found that aqueous agents which compriseioxynil or derivatives thereof and, as emulsifiers, certain alkoxylatedalcohols permit very high penetration of the herbicide into the plant.

The present application therefore provides aqueous agents which compriseioxynil or derivatives thereof and one or more compounds of the generalformula (I)

RO—(C[[H]]₂H₄O)_(n)(C[[H]]₃H₆O)_(m)—R′  (I)

in which RO is an alcohol radical chosen from the group of branched orlinear, saturated or unsaturated monohydric alcohols having 1 to 6carbon atoms, or polyols having 2 to 12 carbon atoms and 2 to 6 hydroxylgroups, and R′ is hydrogen and/or a group —CO—R″, in which R″ is abranched or linear, saturated or unsaturated elkyl radical having 5 to29 carbon atoms, n is a number between 1 and 50 and m is zero or anumber between 1 and 10.

DETAILED DESCRIPTION OF THE INVENTION

The agents according to the invention comprise loxynil and/orderivatives thereof, preferably ioxynil alkyl esters or sodium saltsand/or potassium salts of ioxynil or sulfates and carbonates thereof.Particular preference is given to agents which comprise ioxyniloctanoate or heptanoate.

The alkoxylated compounds of the formula (I) are known substances whichare described, for example, in U.S. Pat. Nos. 2,678,935, 3,539,518,4,022,808 or GB 1,050,497, the disclosure of which also forms part ofthe present application.

The compounds of the formula (I) can be prepared by all methods known tothe person skilled in the art, e.g. by esterification of fatty acidswith alkoxylated methanol, as U.S. Pat. No. 3,539,518 describes. Thisprocess is, however, associated with a number of disadvantages, itproceeds in two stages, the esterification lasts for a very long timeand the products are colored as a result of the high reactiontemperatures. In addition, fatty acid methyl ester ethoxylates preparedin this way have relatively high OH numbers after esterification, whichmay be problematic for some applications. A further possibility involvesthe direct reaction of fatty acid esters with alkylene oxides in thepresence of transition metal catalysts, as described in U.S. Pat. No.4,022,808. Preferably, however, the fatty acid alkyl ester alkoxylatesare prepared by a heterogeneously catalyzed direct alkoxylation of fattyacid alkyl esters with ethylene oxide and/or propylene oxide overcalcined or hydrophobicized hydrotalcites. This synthesis process isdescribed in detail in the laid-open specifications WO 90/13533 and WO91/15441, the disclosure of which also forms part of the presentapplication. The products which form in the processes are characterizedby a low OH number, the reaction is carried out in one stage andpale-colored products are obtained. The fatty acid alkyl esters whichserve as starting materials can be obtained either from natural oils andfats, or be prepared by a synthetic route.

The alkoxylated fatty acid esters contain at least 1 mol of ethyleneoxide groups per mole of ester. Preference is given to compounds of theformula (I) which, per mole of ester, contain 1 to 30 mol of ethyleneoxide. It is preferred that, in addition to the ethylene oxide units,between 1 and 10 propylene oxide groups are also present in themolecule. Preference is also given to those compounds of the formula (I)which contain between 1 and 30 mol of ethylene oxide per mole of esterand 1 to 10 mol of propylene oxide groups. For these mixedethylene/propylene oxide adducts, it is possible to use either thosecompounds which have been reacted with a mixture of ethylene oxide andpropylene oxide, or else compounds which have been reacted in twoseparate steps with ethylene oxide and propylene oxide. The alkoxidesspread themselves randomly over the OH groups present depending on thepreparation process.

If compounds of the formula (I) are used which contain polyols asalcohol radical RO, then the data relating to the amount of ethyleneoxide or propylene oxide units (indices n and m) always relates to theoverall molecule. The exact distribution of the ethylene oxide andpropylene oxide units on the different hydroxyl groups of the polyoldepends, however, as is known, on the synthesis process.

The fatty acid ester radicals —CO—R″ contain alkyl radicals R″ having 5to 29 carbon atoms. Suitable as fatty acid component are natural orsynthetic fatty acids, in particular straight-chain, saturated orunsaturated C₆-C₃₀ fatty acids, including technical-grade mixturesthereof, as are obtainable by fat cleavage from animal and vegetablefats and oils, e.g. from coconut oil, palm kernel oil, soybean oil,sunflower oil, rapeseed oil, cotton wool seed oil, fish oil, beef tallowand lard; specific examples are caprylic, capric, lauric, lauroleic,myristic, myristoleic, palmitic, palmitoleic, oleic, elaidic, arachidic,gadoleic, behenic and erucic acid.

Suitable as alcohol component RO are straight-chain or branched,saturated or unsaturated monohydric alcohols having 1 to 6 carbon atoms,e.g. methanol, ethanol, n- and i-propanol, n- and i-butanol, pentanol,hexanol, 2-ethylhexanol and cyclohexanol. Examples of polyols having 2to 6 carbon atoms which can be used are ethylene glycol, 1,2-propyleneglycol, 1,2-butylene glycol glycerol or trimethylolpropane andpentaerythritol.

In principle, all of the hydroxyl groups of the alcohols are substitutedby the alkoxides, although not all of the terminal alkoxide radicals arecapped with ester groups. If polyols are used as starting alcoholcomponents RO, such as glycerol or ethylene glycol, the agents cantherefore contain either compounds of the formula (I) which are obtainedby reaction of the full esters and also of the partial esters withalkoxides. Preference is, however, given to those compounds of theformula (I) in which all of the hydroxyl groups of the alcohols arealkoxylated and also all terminal alkoxide groups are capped with estergroups of the formula —CO—R″. In these preferred compounds, the radicalR″ in the formula (I) is therefore exclusively a branched or linear,saturated or unsaturated alkyl radical having 5 to 29 carbon atoms.

In the agents according to the invention, preference is also given tousing those alkoxylated fatty acid esters of the formula (I) whose fattyacid component is chosen from linear, unbranched C6 to C₁₈ fatty acidsand whose alcohol component is methanol, where these esters of theformula (I) preferably contain between 1 and 3 mol of propylene oxideand between 1 and 6 mol of ethylene oxide per mole of ester. Suchcompounds can be obtained, for example, by the above-described reactionof palmitic, stearic, oleic, linoleic or linolenic acid lauric andmyristic acid and esters thereof with alkoxides.

Also suitable are alkoxylated compounds in which the alcohol componentused is glycerol and the fatty acid component is chosen from saturatedor unsaturated, branched or unbranched fatty acids having 18 to 22carbon atoms and the esters contain between 1 and 3 mol of ethyleneoxide per mole of ester. Particular preference is given to compounds ofthe formula (I) in which n is 5,10 or 30 and m is zero. Such compoundscan be obtained, for example, by the reaction of glycerol esters ofnatural fatty acids, such as, for example, palm oil, rapeseed oil,soybean oil or, preferably, castor oil, with ethylene oxide.

The compounds of the formula (I) present in the agents according to theinvention are nonionic compounds which can additionally also becharacterized by their HLB value (hydrophilic-lipophilic balanceaccording to the definition by Griffin; see Römpp Lexikon Chemie, 10thedition 1997, page 1764). Preference is given to those agents whichcomprise compounds of the formula (I) with HLB values between 4 and 10and in particular between 5 and 9.

The agents comprise, as herbicidal active ingredients, at least ioxynilor derivatives thereof, although mixtures with other different activeingredients are also possible. The agents according to the invention cancomprise the active ingredient either in enriched form, i.e. the agentsare concentrates with more than 50% by weight to a maximum of 90% byweight of active ingredient. They can, however, also be in dilute form.Preference is given to agents which comprise between 0.01 and 5% byweight of ioxynil or derivatives thereof, based on the weight of theagent. If other agrochemical active ingredients are present, then theseare present in amounts of from 0.01 to 10% by weight. The proportion ofwater in the agents according to the invention is preferably between 10and 99.9% by weight. The quantitative ratio between the compounds of theformula (I) and the active ingredients is preferably between 1:1 and1:100. Particular preference is given to those agents in which theweight ratio between the compounds of the formula (I) and the activeingredients is in the range from 1:10 to 1:80 and in particular in therange from 1:2 to 1:5.

In addition to ioxynil and derivatives thereof and the compounds of theformula (I), the aqueous agents according to the invention can alsocomprise further customary ingredients and additives. These includesolvents, such as ethylene or propylene glycols and C₁-C₆-alcohols,solid carriers, such as lignin, lignin derivatives or clays and furtherknown emulsifiers or dispersants. Particular preference, however, isgiven to those agents which comprise exclusively emulsifiers of theformula (I) and otherwise comprise no further emulsifiers ordispersants. Particular preference is given to those agents which arefree from colloids, such as titanium dioxide, and/or are free fromsolvents, in particular from mineral oil-based solvents.

The agents according to the invention are storage-stable even attemperatures greater than 30° C. and can be prepared without the actionof high shear forces, for example by manual stirring. The agentsaccording to the invention form without the application of strong shearforces, e.g. by simple stirring by hand. The compounds of the formula(I) can be initially introduced for this purpose, for example, in liquidform. The active ingredient is then added and this mixture is dispersedin water. If compounds of the formula (I) with melting points above roomtemperature are used, they can be used in molten form. It is, however,preferable to use those compounds of the formula (I) which have amelting point below 25° C. It is, however, also possible firstly toprepare a mixture of the agrochemical active ingredient in water, andthen to emulsify or disperse this mixture by adding compounds of theformula (I).

Also claimed is a method for controlling undesired plants, where anaqueous ioxynil-containing agent as in the above description is appliedto the leaves of plants by any method known to the person skilled in theart in amounts such that the plants die.

The present invention further provides for the use of the compounds ofthe formula (I) for increasing the penetration of ioxynil or derivativesthereof into the leaves of plants.

EXAMPLES

Six aqueous ioxinyl Na salt emulsions were prepared which were eitherfree from emulsifiers or comprised known emulsifiers, and these werecompared with an agent according to the invention comprising, asadditive, a compound of the formula (I) where RO=glycerol, R′=COR″ whereR″=C16-C18, m=0, n=30.

The emulsifiers were in each case present in amounts of 0.5% by weight,based on the overall agent. The concentration of the sodium salt ofioxynil was 4.1 mM. In each case 0.1 μl of the aqueous agent wereapplied to the first leaves of deadly nightshade. Penetration into theleaves after 24 hours was then measured. The results are given in Table2.

TABLE 1 Experiment Emulsifier (1) — (2) C₆₋₁₀-alkyl (oligo) glucoside(3) C₆₋₁₀ fatty acid methyl ester + 3 EO (4) C₈₋₁₀ fatty acid methylester + 6 EO (5) nonylphenol + 10 EO (6) triglyceride according to theinvention

TABLE 2 Experiment Penetration after 24 hours in % (1) 0 (2) 2 (3) 22(4) 56 (5) 42 (6) 82

The results show the increase in the penetration of the ioxynil as aresult of the addition of the agent according to the invention.

What is claimed is:
 1. A method of increasing the penatration of ioxynilor a derivative thereof into the leaves of a plant comprising the stepsof: (1) forming a composition comprising water and ioxynil and/or aderivative thereof and a compound of the formula (I)RO—(C₂H₄O)_(n)(C₃H₆O)_(m)—R′  (I) wherein RO is an alcohol radicalselected from the group consisting of branched or linear saturated orunsaturated monohydric alcohols having from 1 to 6 carbon atoms, or apolyol radical having from 2 to 12 carbon atoms and from 2 to 6 hydroxylgroup; R′ is hydrogen or an ester group —CO—R″ wherein R″ is a branchedor linear, saturated or unsaturated alkyl radical having 5 to 29 carbonatoms, n is a number between 1 and 50 and m is zero or a number between1 and 10 wherein the amount of the compound at formula I is sufficientto increase the penetration of ioxynil or derivatives thereof into theleaves of a plant; (2) contacting the leaves of a plant with thecomposition.
 2. The method of claim 1 wherein R″ is branched or linear,saturated or unsaturated alkyl radical having from 17 to 21 carbonatoms.
 3. The method of claim 1 wherein RO is a glycarol radical and R″is a branched or linear, saturated or unsaturated alkyl radical havingfrom 17 to 21 carbon atoms.
 4. The method of claim 1 wherein n is anumber between 1 and 30 and m is zero or a number between 1 and
 5. 5.The method of claim 1 wherein n is 5,10 or 30 and m is zero.
 6. Themethod of claim 1 wherein —CO—R″ is a ricinoleic acid radical and RO isa glycerol radical.
 7. The method of claim 1 wherein RO is a methanolradical and R″ is a branched or linear, saturated or unsaturated alkylradical having from 5 to 17 carbon atoms.
 8. The method of claim 1wherein the compounds of the formula (I) has an HLB value between 4 and10.
 9. The method of claim 1 wherein the amount of the ioxynil is from0.01 to 5% by weight.
 10. The method of claim 1 wherein the ioxynilderivative is an alkyl esters.
 11. The agent of claim 10 wherein theioxynil derivative is ioxynil octanoate or ioxynil heptanoate.
 12. Themethod of claim 1 wherein the ioxynil derivative is the sodium saltsand/or potassium salt.
 13. The method of claim 1 is wherein the agent isfree from colloidal material.